ELECTRICAL ENGINEERING DEPARTMENT QUESTION BANK Subject: Electrical Drives and FACTS Devices Subject code: (EE 5003) 1.Define an Electric Drive .What are the diff. factors which affect the selection of drive? 2.Discuss choice of Mill Derive in a cement mill. Also give name and discuss characteristics of motor used as blower drive. 3. Define Converters and Inverters. Showing inverter voltage waveforms, discuss working of pulse width modulation inverter. 4. Discuss Speed control of Induction motors. Also discuss application of power electronic device in above speed control. 5.Discuss a FACT system. What is a FACT –controller? Discuss working of a FACT-controller in power system. 6. Discuss operation of thyristor-controlled series capacitors for transmission lines. 7.What is meant by braking in an Industrial drive? What are types of braking systems? Discuss Dynamic braking for D.C. motors. 8.Define compensation in power system. What is VAR compensation? Discuss thyristor controlled VAR-compensation of transmission lines. 9. Give classification of electric drives. Which one is most preferable and why? 10. What do you mean by AC drives and DC drives? Which are widely used now days and why? 11.Draw the block diagram of Electric Drive system. Explain the function of each block in detail. 12. What are the different DC machines used in drives, explain with help of their characteristics .Also give their applications. 13 What are the different AC machines used in drives, explain with help of their characteristics. Also give their applications. 14. What types of Drives are used in Cement mills and why? 15. What types of Drives are used in Steel mills and why? 16. What types of Drives are used in Textile mills and why? 17. What types of Drives are used in sugar mills and why? 18 What types of Drives are used in Electric traction and why? 19.What are cyclo-converters and how these can be used to control speed of induction motors? 20. What are choppers ? Discuss their applications in electric drives. 21. What are Inverters ? Discuss their applications in electric drives. 22 What are phase control rectifires? Discuss their applications in Electric drives. 23. What are the advantages and disadvantages of using Thyristorised speed control method of drives? 24.Why Volt/Hertz method is prefffered for speed control of Induction motor? What are its advantages and draw different circuits used for it. 25. Draw the static scherbius and static Kramer drive system. How they differ from each other. 26. Why electrical braking is more preferable than mechanical braking? What are the different types of Electrical Braking system? 27. Explain Plugging or counter- current braking in D.C. Machines, Induction Machine and Synchronous Machine. 28. Explain Dynamic or rheostatic braking in D.C. Machines, Induction Machine and Synchronous Machine. 29. Explain Regenerative braking in D.C. Machines, Induction Machine and Synchronous Machine. 30. Explain Regenerative braking in D.C machines using Choppers. 31. How dual converters can be used for ergative braking? 32. What is Pulse width Modulation (PWM)? What are the advantages of using PWM Inverters. 33. What are the different methods of speed control of Induction motor and which power electronic converters can be used for each method? 34 What are the different methods of speed control of DC motors and which power electronic converters can be used for each method? 35. What do you mean by PLC, draw its block diagram and how it is useful in Electric drives? 36. What are different types of FACTS controller used in transmission line? 37. What do you mean by compensation? What is the role of series inductors and series capacitors in compensation? 38. What do you mean by compensation? What is the role of shunt inductors and shunt capacitors in compensation? 39. Explain the concept of Series compensation by two machine transmission model. 40. Explain the concept of Shunt compensation by two – machine transmission model. 41. How FACTS controller is better then other controllers? 42. What are the different types of Series FACTS controller used in T. line? 43. What are the different types of Shunt FACTS controller used in T. line? 44. Explain working of TSSC and TCSC 45. Explain working of FC-TCR. 46. Explain working of GCSC and SSSC. 47. Explain working of TSC-TCR 48. Explain working of TCR, TSC and TSR. 49. What you mean by Static Var System (SVS)? 50. Explain the working of TCBR. What are the objectives of using it? 51. Why series motors are used in Electric traction? 52. What is Active and passive loads. Give their examples. 53. What do you mean by group drive? What are its advantages and disadvantages? 54. What do you mean by Mutimotor drive? What are its advantages and disadvantages? 55. What do you mean by individual drive? What are its advantages and disadvantages? 56. Explain CSI and how they are better then VSI. 57. Explain the principle of Chopper? 58. Name methods used for braking of synchronous motors. Why is plugging method not used for above motors? 59. For what purpose cycloconveters are used in an electric drive? List at least 3-main features of cycloconvertes. 60. Describe Static Resistance speed control method in Induction motor. 61. Describe stator voltage control method for 3-phase I.M. 62. Differentiate between electrical braking and mechanical braking. 63. Draw block diagram of electric drive system. 64. Draw Block diagram of PLC. 65. Explain PWM technique and what are its advantages? 66. A220V, 1500rpm, 10 A separately-exited dc motor has an armature resistance of 1 ohm. It s fed from a single-phase fully-controlled bridge rectifier with an ac source voltage of 230 V, 50 Hz. Assuming continuous load cureent, compute (a) Motor speed at the firing angle of 30 and torque of 5Nm (b) Developed torque at the firing angle of 45 and speed of 1000rpm. 67. A separately excited motor is supplied from 230V, 50 Hz source through a single-phase half-wave controlled converter. Its field is fed through 1-phase semi converter with zero degree firing –angle delay. Motor res =0.7ohm and motor contt. = 0.5 V-sec/rad. For rated load torque of 15 Nm at 1000rpm and fro cont. ripple free currents, determine (a ) firing-angle delay of armature converter (b) rms value of thyristor and freewheeling diode currents. (c ) input power factor of armature converter 68. The speed of 15hp, 220V, 100rpm dc series motor is controlled using a 1-phase half- controlled bridge converter. The combined armature and field resistance is 0.2 ohm. Assuming continuous and ripple free motor current and speed of 1000rpm and k=0.03 Nm/amp2,determine (a) motor current (b) motor torque for a firing angle 30.Ac voltage is 250V. 69. A 220V, 100rpem, 60A separately-excited dc motor has armature res. Of 0.1ohm.Ti is fed from a single-phase full converter with an ac source voltage of 230V, 50Hz.Asuming cont. conduction, and compute. (a) Firing angle for rated motor torque at 600rpm (b) Firing angle fro rated motor torque at (-500) rpm (c) Motor speed fro firing angle 150 and half rated torque 70. The speed of a separately excited dc motor is controlled by means of a 3-phase semi converter from a 3-phase semi converter from a 3-phase, 415V, and 50 Hz supply. The motor constants are: inductance 10mH, resistance 0.9 ohm and armature constant 1.5 V/rad/sec. Calculate the speed of this motor at a torque of 50 Nm when the converter is fired at 45. Neglect losses in the converter. This motor at a torque of 50Nm when the converter is fired at 45 degree. Neglect losses in the converter. 71. The chopper used fro on-off control of dc separately-excited motor has supply voltage of 230V, an on-time of 10msec and off-time of 15 msec. Neglecting armature inductance and assuming continuous conduction of motor current, calculate the average load current when the motor speed is 1500rpm and has a voltage constt of Kv =0.5V/rad/sec. The armature res. Is 3 ohm. 72. A dc chopper is used fro regenerative braking of separately-excited dc motor. The dc supply voltage is 400V. The motor has ra+0.2 ohm, Km+ 1.2V-s/rad. The average armature current during regenerative braking is kept constt. At 300A with neg. ripple. For a duty of 60% for a chopper determine (a) power returned to the dc supply (b) min. and max. permissible braking speeds (c) Speed during regenerative braking. 73. Compare static Sherbius drive and static Kramer drive. 74. Give the concept of Electric drive. Illustrate your answer with example. 75. Give two methods of speed control normally employed fro dc motors. Hence sketch chars. of a separately excited motor based on these methods. Indicate clearly const. torque drive nad cont..-power drive regions. 76. Give general ckt. Layout fro single phase dc drives. Enumerate the various 1-phase dc drives used. 77. Give general ckt. Layout fro single phase dc drives. Enumerate the various 3-phase dc drives used. 78. Describe how the e speed of a separately – excited dc motor is controlled through the use of two 3-phase full converters. Discuss how two-quadrant drive can be obtained from this scheme. Drive expression for rms values of source and thyristor currents. State the assumption made. 79. Distinguish between two quadrant and four quadrant drives. 80. Enumerate the various methods of speed control of 3-phase induction motor when fed through semiconverter devices. 81. Discuss how volt/hertz control for a 3-phase induction motor is similar to armature-voltage control of dc motor. 82 In stator –frequency control of 3-phase induction motor, explain why (i) ratio V/f is maintained constt. For speeds below base speed (ii) terminal voltage is maintained constt. For speeds above base speed. 83. Describe stator current control method for 3-phase I.M. Derive expression for max. torque, slip at max. torque etc. by using apporx. Equiv. circuit. 84. What are inverters? Explain those speed control methods of ac drive where inverters are used. 85. What do you understand by constt. Torque drive and constt. Power drive? 86. When plugging is employed for stopping an induction motor, (a )it is necessary to disconnect it from supply when speed reaches close to zero. Why? (b) usually a external res. Inserted into the rotor circuit. Why? 87. Variable frequency control of IM motor is more efficient than stator voltage control, Why? 88. Why stator voltage control is suitable for speed control of IM motor in fan and pump drives? 89. Why slip-power recovery scheme is suitable mainly for drives with a low speed range? 90. Why a synchronous motor doesn’t have starting torque. 91. What is the role of damper winding in syn. Motor? 92. Explain plugging in case of Induction motor. 93. What are FACTS devices? What is their role in power system? 94. Explain Series FACTS controller. 95. Explain Shunt FACTS controller. 96. Explain TSSC. 97. Explain TCSC. 98. Explain TCR andTSR. 99. Explain TCBR. 100 Explain shunt compensation and series compensation.
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